Gonad development and somatic growth patterns of Olindias sambaquiensis (Limnomedusae, Olindiidae)
The stinging hydromedusa Olindias sambaquiensis (Limnomedusae, Olindiidae) was examined monthly over a 24-month period in Blanca Bay (Buenos Aires, Argentina) in order to determine the relationship between gonad development and overall growth patterns of medusae. Olindias sambaquiensis occurred seasonally from November (spring) to late April (fall). Medusae grew until February (mean bell diameter: 76.2 mm ± 2.8), and began to decrease in diameter up to late April (mean bell diameter: 58.6 mm ± 4.2). From November to December, the gonads of medusae were either undifferentiated or not present (gonad index (GI) 4.9%). Sexually mature individuals were observed from January to late February, where GI increased up to 31.4%, reaching, in some cases, values higher than 70%. From late February to April, O. sambaquiensis spawn and GI decreased to 25%. Highest growth rates were observed during December (immature phase), and then decreased until February (maturation phase). Growth rates were negative throughout March and April (spent phase). Growth patterns of gonads were different from those of the rest of the medusa: (1) their growth rates (and shrinking rates) were higher than those of the rest of the body, and (2) the percent of ‘total organics’ (AFDW: ash-free dry weight) in gonads remained constant, while it decreased in the rest of the body. Medusa length-weight relationships were also affected by gonad weight: a positive allometry was observed only when gonad weight was included into the total weight (i.e., whole individual).
Key words: somatic growth, allometric growth, hydromedusae, Olindias sambaquiensis, Blanca bay, Argentina
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